Macbeth, a play about a regicide and its aftermath, tells the story of the tragic downfall of Macbeth, a noble war hero driven by his overwhelming ambition to rule Scotland. It is both the shortest tragedy ever written by William Shakespeare, and arguably the bloodiest of his plays. From the first act of the play, in which King Duncan learns of how Macbeth has slain the traitorous Macdonwald, to the close of the play, where Macbeth falls at the hands of Macduff, Macbeth depicts one bloody murder after another. There has been much debate about which character is most responsible for the many acts of violence in the play. While the Three Witches' predictions influence Macbeth's thoughts, and plant in his mind the idea that he will be king, and while Lady Macbeth drives and manipulates her husband to murder Duncan, ultimately it is Macbeth, being of sound mind, and of his own free will, who does 'the deed', and is therefore the most responsible for the bloody murder of King Duncan, and the murders that follow in the aftermath.
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The Three Witches' predictions influence Macbeth's thoughts, and plant in his mind the idea that he will be king. In Act I, scene iii, Macbeth and Banquo first meet with the witches, and learn of their prophecies. The witches predict that Macbeth will be Thane of Cawdor, and King of Scotland, and that Banquo's children will also be king. Banquo wonders if he and Macbeth have "eaten on the insane root (I, iii, 82). Macbeth, however, upon learning that he has been made the Thane of Cawdor, takes the witches' third prediction to heart. Seeing Macbeth consumed in thought, Banquo comments, "Look how our partner's rapt" (I, iii, 141). He warns Macbeth not to believe all that the witches say, however, Macbeth doesn't appear to heed his friends remarks. The Three Witches influence over Macbeth's thoughts are also evident when Macbeth considers killing Duncan, and says "I am Thane of Cawdor.